1. Field of the Invention
The present invention relates to fuels, particularly gasoline fuels which contain ethanol. More specifically, the present invention relates to a method of making a summer, low-emission gasoline fuel which contains ethanol and complies with the California Code of Regulations.
2. Brief Description of the Related Art
One of the major environmental problems confronting the United States and other countries is atmospheric pollution caused by the emission of pollutants in the exhaust gases and gasoline vapor emissions from gasoline fueled automobiles. This problem is especially acute in major metropolitan areas where atmospheric conditions and the great number of automobiles result in aggravated conditions. While vehicle emissions have been reduced substantially, air quality still needs improvement. The result has been that regulations have been passed to further reduce such emissions by controlling the composition of gasoline fuels. These specially formulated, low emission gasolines are often referred to as reformulated gasolines. California""s very strict low emissions gasoline is often referred to as California Phase 2 gasoline. One of the requirements of these gasoline regulations is that, in certain geographic areas, oxygen-containing hydrocarbons, or oxygenates, be blended into the fuel.
Congress and regulatory authorities, such as CARB (the California Air Resources Board), have focused on setting specifications for low emissions, reformulated gasoline. The specifications, however, require the presence of oxygenates in gasoline sold in areas that are not in compliance with federal ambient air quality standards for ozone, and the degree of non-attainment is classified as severe, or extreme. Among the emissions which the reformulated gasoline is designed to reduce, are nitrogen oxides (NOx), hydrocarbons (HC), and toxics (benzene, 1,3-butadiene, formaldehyde and acetaldehyde). A reduction in these emissions has been targeted due to their obvious impact upon the air we breathe and the environment in general.
Oxygenated gasoline is a mixture of conventional hydrocarbon-based gasoline and one or more oxygenates. Oxygenates are combustible liquids which are made up of carbon, hydrogen and oxygen. All the current oxygenates used in reformulated gasolines belong to one of two classes of organic molecules: alcohols and ethers. The Environmental Protection Agency regulates which oxygenates can be added to gasoline and in what amounts.
The primary oxygen-containing compounds employed in gasoline fuels today are methyl tertiary butyl ether (MTBE) and ethanol. While oxygen is in most cases required in reformulated gasolines to help effect low emissions, the presence of ethers such as MTBE in gasoline fuels has particularly begun to raise environmental concerns. For example, MTBE has been observed in drinking water reservoirs, and in a few instances, ground water in certain areas of California. As a result, the public is beginning to question the benefits and/or importance of having an ether such as MTBE in cleaner burning gasolines, if the ether simply pollutes the environment in other ways.
Thus, while some of the concerns with regard to gasoline fuels containing ethers, could be overcome by further safe handling procedures and the operation of present facilities to reduce the risk of any spills and leaks, there remains a growing public concern with regard to the use of ethers such as MTBE in gasoline fuels. In an effort to balance the need for lower emission gasolines and concerns about the use of ethers it, therefore, would be of great benefit to the industry if a cleaner burning gasoline without ethers, which complied with the requirements of the regulatory authorities (such as CARB), could be efficiently made.
Replacing ethers such as MTBE with ethanol is one possibility to reducing the use of MTBE. However, the use of ethanol presents other problems, particularly in its handling and transportation. Transporting a gasoline containing ethanol from a refinery to a terminal, particularly through a pipeline, often results in the ethanol picking up water. This results in the final gasoline not meeting the specifications required, e.g., by the California Code of Regulations. As well, rust in the pipeline can be loosened by the ethanol, resulting in further contamination of the gasoline.
The replacement of ethers with ethanol in the blending of gasolines which meet the California Code of Regulations, therefore, still requires the need to resolve several major problems. Because of the importance ethanol is beginning to play in oxygenated gasoline, a resolution of these problems would be of great interest to the industry.
It is therefore an object of the present invention to provide a method of blending ethanol into a gasoline formulation while overcoming the foregoing problems.
It is yet another object of the present invention to provide a novel method for obtaining a gasoline formulation containing ethanol which meets the California Code of Regulations.
Yet another object of the present is to provide a method of blending a gasoline formulation containing ethanol at a site remote from the refinery, which formulation meets the California Code of Regulations.
These and other objects of the present invention will become apparent upon a review of the following description, the figures of the drawing, and the claims appended hereto.
In accordance with the foregoing objectives, there is provided by the present invention a method for blending unleaded gasoline containing ethanol, and having A Reid Vapor Pressure (RVP) in pounds per square inch (psi) of 8.0 or less, and more preferably 7.0 or less. The method comprises providing a substantially oxygenate free unleaded gasoline blend stock which has an RVP of no greater than 7.0, and more preferably no greater than 6.0. Ethanol is then added to the gasoline blend stock in an amount such that the final gasoline meets the California Code of Regulations, with the unleaded gasoline blend stock to which the ethanol is added having a T50 sufficiently high such that the ethanol addition does not cause the T50 value to drop below the ASTM D 4814 minimum requirement of 170xc2x0 F. In a preferred embodiment, the amount of ethanol added is at least 2.0 volume percent based on the final gasoline.
Among other factors, the present invention is based upon the discovery that the addition of ethanol to a gasoline blend stock cannot be a linear addition, for the specifications of the gasoline are changed non-linearly when ethanol is added. The specifications of the gasoline blend stock must therefore be controlled in order to compensate for the addition of ethanol. This is particularly true for the RVP and T50 characteristics of the gasoline. The present invention, therefore, blends ethanol with a gasoline blend stock which has an RVP sufficiency low and a T50 specification sufficiently high such that the addition of the desired amount of ethanol results in a gasoline which is in compliance with the California Code of Regulations. It is the discovery of the need to so control the RVP and T50 specifications of the gasoline blend stock which permits one to successfully blend the ethanol into a compliant gasoline formulation.
In a preferred embodiment, the present invention allows one to blend a gasoline blend stock having predetermined RVP and T50 specifications at a refinery which does not contain ethanol, transport the blend stock through a pipeline to a terminal, and mix the ethanol and blend stock at the terminal with confidence that the final gasoline composition meets the California Code of Regulations. This method allows one to avoid the problems inherent in the transporting of an ethanol containing gasoline formulation, while meeting all required specifications for the gasoline.